This invention relates to an improved maintenance or service station for an ink cartridge of a printer and, more particularly, to an improved maintenance or service station for an ink cartridge of a printer having a portion of its cam surfaces formed with an unique profile and an unique spring arrangement.
U.S. Pat. No. 5,440,331 to Grange discloses a service or maintenance station for an ink cartridge of an ink jet printer. Wiping of the print head of an ink cartridge by wipers on a movable sled occurs at a first elevation to which the movable sled is raised from its lowermost position and capping of the print heads of the ink cartridges occurs at a second and higher elevation of the movable sled. The movable sled is supported in a fixed base having cam surfaces for cooperating with cam followers on the sled to raise and lower the sled.
The cam profiles of the cams are straight line surfaces. These create a need for a relatively large motor, which is driving the carrier, because of the varying forces applied by motion of the sled, which is driven by the carrier, along the cam profiles to its uppermost position.
While the aforesaid Grange patent returns the sled to its lowermost position solely by engagement of the carrier with the sled so as to require a relatively large amount of power, it has been previously suggested to return the sled to its lowermost position through the use of a return spring. This return spring applies a force solely in the direction of longitudinal movement of the movable sled. The return spring reduces the power utilized in comparison with the maintenance or service station of the aforesaid Grange patent. However, the return spring creates substantial noise in the printer when it biases the movable sled to its lowermost position because of engagement of the movable sled with its base.
The maintenance or service station of the present invention satisfactorily solves the foregoing problems. The maintenance or service station has the cam profile designed in accordance with a quadratic equation for the final portion of upward motion of the movable sled along each of the cams. This design of the cam profile reduces the required force to move the movable sled to its uppermost position, which is the position at which there is capping of the print heads on the ink cartridges, to a minimum and a constant. The required force during capping is greater than the force required to move the movable sled upwardly from its lowermost position. Therefore, the design of the final portion of the cam profile in accordance with a quadratic equation lowers power usage and enables a smaller motor to be employed for driving the carrier.
The noise level created by using the previously suggested return spring is decreased in the maintenance station of the present invention. This is accomplished by disposing the return spring so that its force is exerted at an angle to the longitudinal movement of the movable sled.
This diagonal positioning of the return spring produces a first component of the force along the longitudinal movement of the movable sled and a second component of the force perpendicular to the longitudinal movement of the movable sled. The second component of the force urges the front wall of the movable sled into engagement with the front wall of the support housing to create friction therebetween when the movable sled is returned to its lowermost position by the first component of the force of the return spring. This friction along with damping created by a viscous media on the front wall of the support housing absorbs the energy of the return spring. As a result, the left end of the movable sled does not engage the left end of the support housing with as large a force so that the noise level of the printer is reduced.
The second component of the force enables the return spring to also hold the movable sled at a known home position with respect to the support housing. That is, the return spring holds the front wall of the movable sled against the front wall of the support housing to provide the known home position. This enables more precise motion of the movable sled since it is always starting from the same fixed known home position rather than an approximate home position.
An object of this invention is to provide an improved maintenance station for use in maintaining or servicing an ink cartridge of an ink jet printer.
Another object of this invention is to provide a maintenance station having an uppermost portion of a cam profile designed in accordance with a quadratic equation to require a relatively constant minimum force for causing upward movement of a movable sled as it is moved longitudinally.
A further object of this invention is to provide a maintenance station having a return spring, which returns a movable sled to its home position, to produce a force to move the movable sled transversely to a fixed known home position and to have its energy absorbed to reduce the noise level of the printer.
Other objects of this invention will be readily perceived from the following description, claims, and drawings